Conventional endoscopes are supplied with light from an external light source. This source is coupled to the endoscope by means of a detachable fiberoptic cable. Broad spectral energy is transmitted through the fiber optic cable. However, the fiber optic cables are often disconnected from the endoscope while still energized by the light source. It is desirable that the light exiting the fiber optic cable be attenuated when the fiber optic cable is disconnected from the endoscope.